The invention relates generally to processes for electrographic image development.
Processes for developing electrographic images using dry toner are well known in the art and are used in many electrographic printers and copiers. The term “electrographic printer,” is intended to encompass electrophotographic printers and copiers that employ a photoconductor element, as well as ionographic printers and copiers that do not rely upon a photoconductor. Electrographic printers typically employ a developer having two or more components, consisting of resinous, pigmented toner particles, magnetic carrier particles and other components. The developer is moved into proximity with an electrostatic image carried on an electrographic imaging member, whereupon the toner component of the developer is transferred to the imaging member, prior to being transferred to a sheet of paper to create the final image. Developer is moved into proximity with the imaging member by an electrically-biased, conductive toning shell, often a roller that may be rotated co-currently with the imaging member, such that the opposing surfaces of the imaging member and toning shell travel in the same direction. Located adjacent the toning shell is a multipole magnetic core, having a plurality of magnets, that may be fixed relative to the toning shell or that may rotate, usually in the opposite direction of the toning shell.
The developer is deposited on the toning shell and moved into proximity with the imaging member, at a location where the imaging member and the toning shell are in closest proximity, referred to as the “toning nip.” In the toning nip, the magnetic carrier component of the developer forms a “nap,” similar in appearance to the nap of a fabric, on the toning shell, because the magnetic particles form chains of particles that rise from the surface of the toning shell in the direction of the magnetic field.